The present invention relates to a method of and apparatus for adjusting the blade of a cutter drum. More particularly this invention concerns to the adjustment of a blade of a cutter drum used for reducing pieces of wood to chips or the like suitable for the production of chip board, laminates, and the like.
A cutter for a wood-chipping apparatus normally has a cylindrical drum on whose periphery is mounted a plurality of angularly equispaced blades. Each of these blades has an outer cutting edge which defines a line that extends at a slight angle to the axis of rotation of the drum, but which lies in a plane parallel to the rotation axis of the drum. Each of these blades furthermore is formed as a flat bar and has a planar surface terminating at the respective cutting edge. This surface itself defines a plane that extends non-radially of the surface, normally inclined into the direction of rotation of the drum.
In order to achieve most uniform chipping with such a drum it is essential that the cutting edges of the blade all lie on the same desired ideal orbit that is centered on the rotation axis of the drum. This orbit can be a frustocone but is almost always a cylinder. If a blade projects beyond this orbit it will wear very rapidly, as it will be the first blade to contact the workpiece, and if a cutting edge lies within the orbit it will never come into contact with the workpiece so that the other cutting edges will do all of the cutting.
For adjustment it is typical to provide an arrangement such as described in the above-identified copending patent application wherein the blades can be mounted in grooves in the surface of the drum and held loosely in place during an adjustment operation. Once the blades are adjusted and properly positioned with their cutting edges lying exactly on the desired orbit, the clamping force is increased in order to lock them tightly in place.
A device is known for carrying out this adjustment operation which comprises a beam or bar having a planar face. This bar is mounted on one or more arms pivoted about an axis which is parallel to the cutting edge of a blade being adjusted. This beam is pivoted into a position where the point of contact between it and a blade being adjusted lies on a line joining the pivot axis for the beam and the rotation axis for the drum. Thus the beam is rotated into this position and the drum is moved past it, thereby pushing the blade into the desired position which is defined by the surface of the beam, this surface lying in a plane parallel to the rotation axis of the drum in the adjustment position.
Such an arrangement has the considerable disadvantage that it applies forces to the blade which tend to remove its edge. Furthermore it is necessary to allow for axial sliding of the surface of the beam relative to the support for this beam, as relative rotation of the drum and beam past each other would cause complete destruction of the cutting edge of the blade being adjusted if such a sliding were not allowed.
Another disadvantage of the known devices is that they are frequently in the way when the machine is in use, limiting access to it and often being fouled with debris. Furthermore they cannot readily be adjusted for different settings of the cutting blades.